The present invention relates to a controllable pitch propeller, particularly for boat drive, which includes a rotating driven hub and propeller blades positioned thereon in adjustable manner, and an adjustment device having an adjustment ring that can move axially and to which adjustment bars for the propeller blades are attached. At least one continuous exhaust gas channel is positioned in the hub.
Controllable pitch propellers of this type are known (EP-A-02 31 503, US-A-47 44 727). They are used on outboard engines with Z-type propellers, and also with direct bedding in the hull. Their size is such that they can replace a customary propeller with fixed propeller blades. Since Z-type propellers require large hub diameters, the exhaust gases of the drive engine are led through the interior of the hub, which is constructed as a waste-gas channel.
In controllable pitch propellers of the generic type initially described, forces for adjusting the propeller blades are applied from outside to the lever bars positioned on the adjustment ring. Thus the adjustment forces are external forces that are transmitted together with the propeller thrust forces generated by the propeller blades to a hub bearing. Since in an adjustment device of this type the adjustment forces are almost as great as the thrust forces, not only the force-conveying parts of the hub but also the hub bearing must be of an appropriate size. This can lead to considerable problems, particularly in small embodiments.
For controllable pitch propellers for ocean-going vessels, it is known that an hydraulic fluid is introduced into the propeller hub to activate a piston system positioned in the hub, which piston system adjusts the propeller blades (US-A-29 31 443).